The effects of and the interplay between natural and anthropogenic influences on the composition of benthic communities over long time spans are poorly understood. Based on a 160-cm-long sediment core collected at 44 m water depth in the NE Adriatic Sea (Brijuni Islands, Croatia), we document changes in molluscan communities since the Holocene transgression ~11,000 years ago and assess how they were shaped by environmental changes. We find that (1) a transgressive lag deposit with a mixture of terrestrial and marine species contains abundant seagrass-associated gastropods and epifaunal suspension-feeding bivalves, (2) the maximum-flooding phase captures the establishment of epifaunal bivalve-dominated biostromes in the photic zone, and (3) the highstand phase is characterized by increasing infaunal suspension feeders and declining seagrass-dwellers in bryozoan-molluscan muddy sands. Changes in the community composition between the transgressive and the highstand phase can be explained by rising sea level, reduced light penetration, and increase in turbidity, as documented by the gradual up-core shift from coarse molluscan skeletal gravel with seagrass-associated molluscs to bryozoan sandy muds. In the uppermost 20 cm (median age <200 years), however, epifaunal and grazing species decline and deposit-feeding and chemosymbiotic species increase in abundance. These changes concur with rising concentrations of nitrogen and organic pollutants due to the impact of eutrophication, pollution, and trawling in the 20th century. The late highstand benthic assemblages with abundant bryozoans, high molluscan diversity, and abundance of soft-bottom epi- and infaunal filter feeders and herbivores represent the circalittoral baseline community largely unaffected by anthropogenic impacts.

中文翻译：

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由全新世海平面上升和近期人类富营养化和污染形成的布里俄尼群岛（亚得里亚海北部）的软体动物底栖群落

人们对自然和人为影响在很长一段时间内对底栖群落组成的影响及其相互作用知之甚少。基于在 NE 亚得里亚海（克罗地亚布里俄尼群岛）44 m 水深收集的 160 厘米长的沉积物核心，我们记录了自大约 11,000 年前全新世海侵以来软体动物群落的变化，并评估它们是如何被环境塑造的变化。我们发现 (1) 陆生和海洋物种混合的海侵滞后沉积物含有丰富的海草相关腹足类动物和表层悬浮摄食双壳类动物，(2) 最大洪水阶段捕获了以表层动物双壳类动物为主的生物基质的建立光区，(3) 高位阶段的特点是在苔藓动物-软体动物泥质砂岩中，下层悬浮饲养者增加，海草栖息者减少。海侵阶段和高位阶段之间群落组成的变化可以通过海平面上升、光穿透减少和浊度增加来解释，如从粗粒软体动物骨骼砾石与海草相关软体动物到苔藓动物的逐渐向上转变所记录的那样沙泥。然而，在最上层 20 厘米（中位年龄 <200 岁），表层动物和放牧物种减少，而以沉积物为食和化学共生物种的数量增加。由于 20 世纪富营养化、污染和拖网捕捞的影响，这些变化与氮和有机污染物浓度的上升相一致。